TEMPERATURK. 



evfn from thofif parts of the furface of the earth where the 

 circumilances are mod f.ivourable to radiation, the quantity 

 radiated cannot be equal to the quantity received from the folar 

 rays. Over the whole earth llic diffufion muft be ftill 

 greater ; and inftead of the conclufion, that the planet dif- 

 chargcs its excefs of heat by radi.ilion, there is every reafon 

 to draw the oppofite cojiclufion, that part of the heat which 

 it receives from the fun is retained. He further infers, that 

 the temperature of the globe muft rife, from the mode in 

 which heat is communicated to it by the fun ; and at the 

 fame time, as it advances, mull become more equal over the 

 whole furface. And this rife has its limits. There cannot 

 be either unlimited increafe of heat, or unlimited refrigera- 

 tion ; but the final refult will be a ftatc of permanence and 

 uniformity, the continuance of which is fecured by the veiy 

 circumftance, that if it is deviated from, this deviation muft 

 correft itfelf by an increafe of radiation from the hotter 

 parts, or from an increafed abforption of caloric by the 

 colder parts of the globe. According to this theory, in 

 procefs of time, the equatorial and polar parts of the globe 

 will arrive at the fame degree of temperature, which wiU re- 

 main ftationary, as there will be no circulation of heated air 

 or water to the poles. To this reafoning we coneeive it may 

 be objected, that it affumes, without fufficient grounds, that 

 caloric cannot pafs from the earth into unlimited fpace, and 

 that the folar heat does not become latent by chemical union 

 with terreftrial fubftances. It affumes alfo, that caloric is 

 a diftinft fpeciiic fubftance ; an opinion which is denied by 

 fome of the moil eminent philofophers. Nor have we, per- 

 haps, any evidence to prove that the temperature of the 

 earth has changed fince the earlieft records of hiftory, if we 

 except the local changes which refult from drainage and 

 cultivation. It is well known that the climate of Europe 

 is materially changed fince the periods of ancient hiftory, 

 when the Danube was annually frozen, and would admit 

 the paflage of armies over the ice. The climate of the 

 United States of America has alfo undergone a material 

 change during the laft century. Both thefe local changes 

 have been produced by the fame caufe, the deftruftion of 

 extenfive woods, and the progrefs of agriculture ; but, in- 

 dependently of local caufes, we have no data to infer that 

 the temperature of the globe is increafing or diminiftiing. 



Temperature of the Sea. The temperature of the fea 

 near the furface is affefted by the changes of tempera- 

 ture of the atmofphere, and by the currents which tra- 

 verfe it. The currents which flow from the equatorial to 

 the polar regions, fervc to equalize the heat of different lati- 

 tudes. This is remarkably the cafe with the current called 

 the Gulf ftream, which paffes by the fhores of Mexico, 

 Louifiana, and Florida, and round the point of the peninfula, 

 under the fhelter and proteaion of the Bahama illands, which 

 break the efforts of the ocean and the current of the trade 

 wind. This ftream, on entering the ocean, preferves its 

 water by the velocity of its current, and may be further dif- 

 tinguilhed by its colour and temperature. The temperature 

 is from eleven to twenty -two degrees higher than that of the 

 ocean. From the Floridas to Newfoundland the current 

 continues increafing in breadth, and diminifhing in velocity. 

 Some experiments made by Mr. Jonathan Williams, give the 

 difference of temperature between the Atlantic ocean and the 

 Gulf ftream as under, December, 1789. 



Soundings in fhoal-water, on the coaft, 



A httle before entering the ftream, 



In the ftream, .... 



Before reaching Newfoundland, in the ftream, 



At Newfoundland, out of the ftream, 



Beyond the banks, in the open fea. 



Fal.r. 



60 



70 

 66 



54 

 60 



Fal.r. 

 On approaching the coail of England, - 48'- 



Capt. Billings, in 1791, found the temperatureof) ^ 



the lea on the coaft of America, - -J 



In the water of the Gulf ftream, - "77 



In winter, Mr. WiUiams found the variation between the 

 Gulf ftream and the ocean 23°; the difterence, as might be 

 expefted, being kfs in fumraer than in winter. Thefe inqui- 

 ries have afcertaincd another faft, from whence navigators 

 may derive fome advantage ; for by examuiing the tempera- 

 ture of the fea in different places, it has been found that the 

 water is colder in proportion to its Ihallownefs ; and hence 

 may be derived an indication of the approach to land, or to 

 a fhoal. Out of the reach of currents, a difference always 

 exifts between the temperature of the furface and the lower 

 parts of the fea. In northern latitudes, the furface is fome- 

 times warmer and fometimes colder than the lower parts ; 

 but near the equator, the temperature of the furface may be 

 expefted to be invariably warmer than at great depths. In 

 all probability, the temperature of the fea is permanent in 

 each degree of latitude, at a certain depth. Capt. Ellis let 

 down a fea-gage in N. lat. 25° 13'. W. long. 25° 12'. 

 He found the fea falter and colder in proportion to the 

 depth, till the gage had defcended 3900 feet, when the mer- 

 cury in the thermometer came up at 53° ; but the water did 

 not gfrow colder, though he let down the gage 1400 feet 

 lower. At the furface of the fea, the thermometer ftood at 64°. 



From the experiments of Capt. Douglas, near the coafte 

 of Lapland and Norway, of which an account is given in the 

 60th volume of the Philofophical Tranfaftions, the follow- 

 ing differences were obferved between the temperature of the 

 fea at the furface, and at certain depths. 



From 



